Tamper-proof time interval recording system

ABSTRACT

A tamper-proof time interval (i.e., engine operating hours) recording system. An elapsed-time recorder actuated in response to engine oil pressure is enclosed and securely protected from tampering by a protective enclosure. A mounting arrangement secures the enclosure to the engine or other apparatus as to which operating time is to be recorded. The system includes an oil pressure conduit adapted to be connected between the enclosure and the apparatus for causing operation of the recorder in response to operation of the apparatus (e.g., operation of an internal combustion engine thereof). A connector arrangement connects the conduit between enclosure and apparatus so as substantially to prevent nondestructive disconnection of the conduit following connection thereof.

aitet [1 1 States Paul, Sr.

[ Dec. 24, 1974 [54] TAMPER-PROOF TIME INTERVAL RECORDING SYSTEM 22 Filed: oa.26,1971 211 Appl. No.: 192,526

52 us. c1 73/115, 138/114, 285/321, i 1 285/DIG. 22 51 Int. Cl GOlm 15/00, F161 13/00 [58] Field of Search 73/115,391, 201; 137/552.7; 285/321, DIG. 22,340, 175;138/114 [56] References Cited UNITED STATES' PATENTS .j 1 861,828 I 7/1907 Grindrod et a1. 285/175 2,633,404 3/1953 Hathaway 73/391 X 2,838,074 6/1958 Lauck 138/114 X 3,365,939 1/1968 Barber... 73/115 3,429,596 2/1969 Marshall 285/340 3,434,744 3/1969 Yoke et al. 285/340 X FOREIGN PATENTS OR APPLICATIONS 330,960 8/1958 Switzerland l38 /ll4 Primary Examine r-Richard C. Queisser Assistant Examiner-Stephen A. Kreitman Attorney, Agent, or Firm Koenig, Senniger, Powers and Leavitt 57 ABSTRACT A tamper-proof time interval (i.e., engine operating hours) recording system. An elapsed-time recorder actuated in response to engine oil pressure is enclosed and securely protected from tampering by a protective enclosure. A mounting arrangement secures the enclosure to the engine or other apparatus as to which operating time is to be recorded. The system includes an oil pressure conduit adapted to be connected between the enclosure and the apparatus for causing operation of the recorder in response to operation of the apparatus (e.g., operation of an internal combustion engine thereof). A connector arrangement connects the conduit between enclosure and apparatus so as substantially to preventnondestructive disconnection of the conduit following connection thereof.

16 Claims, 7 Drawing Figures ill . I TEE-moor INTERVAL RECORDING SYSTEM BACKGROUND OF THE INVENTION This invention relates to apparatus for recording operating time intervals and more particularly to tamperresistant apparatus for recording hours of engine operations in response to engine oil pressure. In'the operation of certain kinds of engine-driven machinery such as earth-moving and fann tractors, it is often essential to record the hours of operation of internal combustion engines used to power the equipment in order to be able to determine charges for the use of the equipment, to ascertain serviceintervals, to indicate the termination of the warranty period for the equipment, or the like. For such purposes, it has long been conventional to use engine operating hour recorders, particularly elapsed-time meters.

A serious problem in the use of elapsed-time meters on such equipment has been one of unauthorized tampering. In the use of rental equipment, for example, tampering with the meter to prevent its ordinary or fulltime operation may result in lower rental charges; Similarly, there may be tampering in order-to prevent lapse of a warranty period.

Such elapsed-time meters are typically electrically powered. An electrically powered meter may conventionally be actuated, for example, byenergizing an engine ignition circuit. However, the external electric ae tuating circuit can easily be tampered with. Vibrationresponsive meters have been employed where there is not excessive shock and vibration. But, while needing no external actuating circuit, vibration-responsive meters are not dependable where they are subject to severe vibration and shock as in heavy construction and farm machinery. In addition, vibration during shipment could result in erroneous indications of operating time with this kind of meter.

Another prior art arrangement involves enclosing an electrically operated hour meter in'an enclosure secured to the equipment together with a battery and actuating the meter by means of a pressure switch in the enclosure and which is responsive to engine oil pres sure, there being an oil pressure connection between the engine and enclosure. It has heretofore been proposed to employ a locked enclosure. However, this requires a system of locks and keys which is not satisfactory to manufacturers or owners. Moreover, there maystill be the possibility that one may defeat the meter by clamping the oil pressure conduit or by simply disconnecting the conduit and temporarily plugging the oil pressure fitting.

SUMMARY OF THE INVENTION Among the several objects of the invention may be whose operating time is to be recorded; and the provision of such a system which is simply and economically manufactured. Other objects and features will be in part apparent and in part pointed out hereinafter.

Briefly, a tamper-proof time interval recording system includes an elapsed-time recording instrument noted the provision of a substantially tamper-proof re- 4 cording system and specifically the provision of such a system for recording the operating time of apparatus with which the system is used; the provision of such a system for recording the operating time of a pressurelubricated engine; the provision of such a, system having an internal recording instrument but which does not require an external electrical actuating circuit for the instrument; the provision of such a system including a substantially tamper-proof enclosure for the recording instrument but which requires no lock-and-key arrangement; the provision of such a system which, foladapted for being operated in response to fluid pressure and a protective enclosure for the recording instrument, this enclosure when intact securely protecting the instrument from tampering. The enclosure is adapted for being secured to apparatus with regard to which an operating time is to be recorded by the instrument. The enclosure is secured by a special bracket to the apparatus. A relatively flexible conduit is adapted to be connected for providing fluid pressure communication between the recording instrument and the apparatus to cause operation of the instrument in response to operation of the apparatus. The conduit resists twisting of one end thereof with respect to the other. A connector arrangement includes respective threaded fitting at the ends of the conduit for being respectively threadedto provide connections at the enclosure and at the apparatus. The fittings each have the same thread direction orientation. Thus, when both are threaded to provide the connections, neither of the fittings may be tumed in a direction to cause unthreading by loosening thereof without causing tightening of the other fitting. Preferably, the conduit is specially constructed to substantially prevent clamping of the conduit from interrupting the pressure communication. Preferably, also, the conduit includes a plug-andreceptacle arrangement, the plug being receivable by the receptacle following threading of the fittings. The

plug and receptacle cooperate to prevent removalof the plug from the receptacle, when received thereby, and to prevent twisting of the plug and receptacle with respect to one another.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 5 is a cross-sectional elevation of a plug-andreceptacle assembly of the invention;

FIG. 6 is an elevation partly in cross section of a portion of a conduit of the system, as constructed in accordance with the invention; and

FIG. 7 is a lateral cross section of the conduit illustrating the effect of clamping thereof.

' Corresponding reference characters indicate correspending parts throughout the several views of the drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. 1, a tamper-proof recording system of the invention is designated generally 11. The system includes a conventional electrically driven elapsed-time meter 13 having a readout window 15 indicating, for example, a total number of hours and tenths of hours. Meter 13 is enclosed within a rectangular protective enclosure 17. Enclosure 17, which may be of welded steel, for example, must be of construction which, when intact, will securely protect meter 13 from tampering. Enclosure 17 is adapted for being relatively permanently securedby a bracket 19 to apparatus with regard to which operating time is to be recorded by meter 13. Such apparatus may be constituted by a diesel crawler-type tractor, for example. It is contemplated that the system may be used with different types of apparatus and record a parameter (other than operating time) associated with the apparatus. Enclosure 17 includes a rear cover 20 which may be spot-welded in place, being thereby difficultly removable.

Interconnected between .the engine, a portion of which is designated 27, of the apparatus and enclosure 17 is an oil pressure conduit indicated generally 23, this conduit being connected by means of elbow fittings and 26 for providing oil pressure communication between a conventional pressure-responsive switch 24 (FIG. 4), located withinthe enclosure, and the engine 27 for causing recording by meter 13 of engine operation intervals. For this purpose, elbow 25 communicates as in conventional with an oil gallery of engine 27, it being understood that oil pressure will be present during operation of the engine, such pressure closing the pressure switch to connect meter 13 in a series circuit with a heavy-duty, long-lasting battery 29 (see FIG. 4) within enclosure 17, thereby causing meter 13 to accumulate and display a total number of hours at window 15 which represents the total time of operation of engine 27.

In accordance with this invention, conduit 23 is connected between enclosure 17 and engine 27 by a special connector arrangement which substantially prevents nondestructive disconnection of conduit 23 once it has been connected and requiring a destructive disconnection, i.e., cutting of a fitting or the conduit itself, once connected, in order to permit opening (i.e., disassembly) of enclosure 17. The arrangement is such that tampering internally of enclosure 17 and ordinary disconnection of conduit 23 for the purpose of defeating operation of meter 13 are both effectively precluded.

As installed for operation, enclosure 17 is shown in FIG. 2 as secured by bracket 19 to the apparatus or engine 27 with which the system is used. Bracket 19, as shown in FIG. 3, includes a flat rear portion 31 of shape corresponding generally to the plan of enclosure 17 and the two side portions 33 and 35 each adapted to extend along the opposite sides of enclosure 17. Bracket 19 may be secured, as by welding (welds being designated 37) to the apparatus or engine 27. Alternatively, rear portion 31 may be bolted to the apparatus but, in either case, is thus substantially permanently attached.

Enclosure 17 is secured to bracket 19 between side portions 33 and 35 thereof as by means of bolts 39 which extend through respective apertures 41 in side portions 33 and 35. Side portion 33 includes a relatively large additional aperture 42 which, when enclosure 17 is secured to bracket 19, is generally aligned with a receptacle, generally indicated at 43, at the adjacent surface of the enclosure.

A plug designated generally 45 is receivable by receptacle 43 to connect conduit 23 to enclosure 17. Plug 45 and receptacle 43 are designed to cooperate to prevent removal of plug 45 from receptacle 43, when received thereby, so long as enclosure 17 remains intact. For this purpose, plug 45 carries a serrated snap ring 47 which acts as a latch means preventing removal of the plug by expanding within the receptacle behind a shoulder 49 (FIG. 5) of the receptacle.

The snap ring 47 is carried in a groove 51 of a tubular nose portion 53 of the plug. Nose portion 53 carries 0- ring seals 55 which seal the nose portion within a short tube 57 which is connected at one end to the receptacle 43 by means of a sleeve 59 threaded onto a flanged collar 61 of the receptacle. Collar 61 extends through the wall 63 and is secured in position by the sleeve 59. A fitting 65 is carried at the opposite end of tube 57, pressure switch 24 being threaded into the latter fitting. The body of plug 45 is designated 67 and includes a flange 69 which abuts against the flanged collar 61 of the receptacle. Flange 69 includes a pair of pins 71 fit,- ting into apertures 73 of collar 61 to prevent twisting of the plug and receptacle with respect to one another. Thus, as will be apparent, once inserted plug 45 cannot be turned with respect to receptacle 43 until sleeve 59 is unthreaded from collar 61 to provide access to snap ring 47.

The body 67 of plug 45 includes a threaded recess 75 into which is screwed the conventional elbow fitting previously indicated at 26. Conduit 23, which comprises a length of conventional wire-braid hydraulic hose material 77, includes a conventional fitting 79 adapted to the threaded into elbow 26. A similar fitting 81 is shown in FIG. 1 threaded into elbow 25 attached at apparatus or engine 27. Both fittings 79 and 81 have the'same thread direction orientation (e. g., both having a conventional right-hand thread) for a purpose explained below. It will be understood that the hose material 77, while being sufficiently flexible to bend, e.g., as shown in FIG. 1, is of sufficient thickness and strength to resist and prevent any substantial twisting thereof (thus permitting only slight twisting of one end thereof with respect to the other end). Accordingly, when fittings 79 and 81 are threadedto respective elbows 26 and 25 (as in FIG. 1) and plug 45 is plugged into (and retained by) receptacle 43, neither of fittings 79 and 81 may be turned in a direction to cause unthreading by loosening thereof without causing tightening of the other fitting.

Referring to FIG. 6, the construction of one end portion of conduit 23 is shown in detail, the other end being of identical construction. Fitting 79 is shown as having a threaded portion 83 (with the usual right-hand thread) and a tubular portion 85 having a bore 87 providing oil pressure communication. The wire-braid reinforced length of elastomeric material 77 is fitted over tubular portion 85 and a swaged shell 89 secures the length of material 77 in place. A so-called BX or spiral type flexible armor sheath 90 may optionally be applied to conduit 23 for protection of the conduit from abrasion, etc., and to discourage clamping of the conduit.

In accordance with this invention, a length of steel tubing 91 is inserted within the bore '93 of the length of hose material 77 during assembly of the conduit. Tubing 91 has an outside diameter which is preferably slightly less than the inside diameter of hose material 77. Tubing 91 is not necessarily joined or connected to tubular portion 85 (or to the corresponding portion at the opposite end of the conduit) but instead its length preferably is just sufficient that the ends thereof are generally adjacent (or may abut) such tubular portions at the ends of the conduit.

Tubing 91 is substantially nondeformable (except when clamped with exceedingly high force) and has the purpose of substantially precluding and clamping of conduit 23, in an attempt to prevent operation of meter 13, from interrupting the oil pressure cormnunication provided by the conduit between engine 27 and oil pressure-responsive switch 24. It may be observed that tubing 91, while of sufficient strength to preclude outright flattening by ordinary clamping thereof, is nonetheless resilient so as to permit flexing of conduit 23 as illustrated in FIG. 1. FIG. 7 is illustrative of clamping of conduit 23 by the application of forces F from opposite sides of the conduit, causing deforming of the hose material 77 but not tubing 91 and thus leaving voids at 93 (and within the bore of tubing91) permitting continued pressure communication. It will be apparent that a solid length of substantiallynondeformable material may be used in place of tubing 91 and which, though having no bore, nonetheless leaves voids upon clamping of the conduit through which the oil pressure may be communicated. v

In installing and using the system, it is to be understood that bracket 19 may be welded or bolted to the apparatus (e.g., the frame of a crawler tractor) or to engine 27, as during assembly of the apparatus by the manufacturer. Conduit 23, with plug 45 attached to it, may then be connected to engine 27 by threading fitting 81 into elbow 25. Enclosure 17 (which may first be provided with battery 29 and then have its'rear cover 20 spot-welded in place to be difficultly removable) is then positioned between the side members 33 and 35 and bolts 39 then inserted to. secure the enclosure in place. Plug 45 is thereafter inserted into receptacle 43 from which it cannot then be nondestructively removed. The plug is also prevented from being turned with respect to the receptacle. Hence, when so connected, the conduit 23 or its fittings cannot be disconnected without being destroyed, noting that any attempt to loosen either of fittings 79 and 81 results in tightening of the other. Moreover, since plug 45 passes through aperture 42 of bracket 19, enclosure 17 cannot be removed from the bracket. Consequently, tampering with the system to prevent normal recording operation thereof is precluded.

To remove enclosure 17 and gain access to it (as for ultimately replacing battery 29 after thousands of hours of operation), it is necessary'to saw through elbow fitting 26 (requiring a new fitting for reassembly). Enclosure 17 may then be removed from bracket 19, the welds or other means securing rear cover 20 broken or removed, and sleeve 59 loosened to provide access to snap ring 4750 as to permit removal of plug 45. Such steps are so substantial an impediment to tampering as to preclude it. Lead seal wires may also be used through drilled heads of bolts 39 ment to tampering.

In view of the above, it will be seen that the several objects of the invention are achieved and other advantageousresults attained.

As various changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. A tamper-proof recording device comprising:

a parameter recording instrument;

a protective enclosure for said instrument, said enclosure when intact securely protecting said instrument from tampering, and adapted for being secured to apparatus with regard to which a parameteris to be recorded by said instrument;

means for'securing said enclosure to said apparatus;

as an added impedia conduit adapted to be connected for providing communication between said instrument and said apparatus to cause recording by said instrument of said parameter in response to operation of said apparatus; and

connector means for connecting said conduit between said enclosure and said apparatus. so as substantially to prevent nondestructive disconnection of said conduit following said connecting thereof, said conduit comprising a length of tubular material, said material 'being relatively flexible but resisting any substantial twisting thereof, said con nector means comprising respective threaded fittings at opposite ends of said material for being respectively threaded to connections at'said enclosure and said apparatus, said fittings each having the same thread direction orientation whereby when both are threaded neither of said fittings may be turned in a direction to cause unthreading by loosening thereof without causing tightening of the other fitting. g v l 2. A tamper-proof recording device as set forth in claim 1 wherein said conduit must be destructively disconnected, following connection thereof between said enclosure and said apparatus, to permit disassembly of said enclosure. v I

3. A tamper-proof recording device as set forth in claim 1 wherein said connector means comprises a plug and a receptacle, said plug being receivable by said receptacle to connect said conduit to said enclosure, said plug and receptacle cooperating to prevent removal of said plug from said receptacle, when received thereby, while said enclosure is intact.

4. A tamper-proof recording device set forth in claim 3 wherein said plug is carried at one end of said conduit, said receptacle being positioned at a surface of said enclosure, said plug including latch means preventing removal of said plug from said receptacle when received thereby.

5. A tamper-proof recording device as set forth in claim 4 wherein said latch means comprises a snap ring, said snap ring expanding in said receptacle to prevent removal of said plug and being releasable only from within said enclosure.

6. A tamper-proof recording device as set forth in comprises a bracket element adapted for substantially permanent attachment to said apparatus and having an aperture generally in alignment with said receptacle, said conduit passing through said aperture when said plug is received by said receptacle to prevent removal of said enclosure from said apparatus.

7. A tamper-proof recording device as set forth in claim 1 wherein the instrument is an elapsed-time meter, said enclosure including means responsive to fluid pressure for causing operation of said meter, said conduit providing fluid pressure communication between said apparatus and the fluid pressure-responsive means.

8. A tamper-proof recording device as set forth in claim 1 wherein said conduit provides fluid pressure communication between said apparatus and a fluid pressure-responsive means included in said enclosure and wherein said tubular material is relatively compressible and elastic and wherein said conduit further includes a length of relatively incompressible yet flexible tubular material extending through the bore of the compressible tubular material whereby clamping of said conduit causes substantial deformation of only said compressible tubular material and said clamping is substantially precluded from interrupting said fluid pressure communication.

9. A tamper-proof recording device as set forth in claim 1 wherein said conduit provides fluid pressure communication between said apparatus and a fluid pressure-responsive means included in said enclosure and wherein said tubular material is relatively compressible and elastic and wherein said conduit further includes a length of relatively incompressible yet flexible material extending through the bore of said tubular material and having a generally circular cross section of outside diameter less than the diameter of said bore, whereby upon the application of compressive forces to said conduit the tubular material may engage both sides of the incompressible material in the plane of said compressive forces but will not completely engage the entire circumference of said incompressible material so that interruption of said fluid pressure communication is substantially precluded.

10. A tamper-proof recording device as set forth in claim 9 wherein the incompressible material comprises steel tubing.

11. A tamper-proof recording device as set forth in claim 7 wherein said elapsed-time meter is electrically powered, said enclosure including an electric power source for powering said meter, the fluid pressureresponsive means comprising a fluid pressure switchconnected in a circuit with said power source and said meter.

12. A tamper-proof time interval recording device comprising:

an elapsed-time recording means adapted for being operated in response to fluid pressure;

a protective enclosure for said recording means, said enclosure when intact securely protecting said recording means from tampering, and adapted for being secured to apparatus with regard to which an operating time is to be recorded by said recording means;

means for securing said enclosure to said apparatus;

a relatively flexible conduit adapted to be connected for providing fluid pressure communication between said recording means and said apparatus to cause operation of said recording means in response to operation of said apparatus, said conduit resisting twisting of one end thereof with respect to the other; and

connector means including respective threaded fittings at the ends of said conduit for being respectively threaded to provide connections at said enclosure and at said apparatus, said fittings each having the same thread direction orientation whereby when both are threaded to provide said connections neither of said fittings may be turned I in a direction to cause unthreading by loosening thereof without causing tightening of the other fitting.

13. A tamper-proof time interval recording device as set forth in claim 12 further comprising means for substantially preventing clamping of said conduit from interrupting said pressure communication.

14. A tamper-proof time interval recording device as set forth in claim 12 wherein said connector means comprises a plug and a receptacle, said plug being receivable by said receptacle following threading of said fittings, said plug and receptacle cooperating to prevent removal of said plug from said receptacle, when received thereby, and to prevent twisting of said plug and receptacle with respect to one another.

15. A tamper-proof recording device as set forth in claim 8 wherein the length of incompressible tubular material is shorter than the length of compressible tubular material with the outside diameter of the former being less than the inside diameter of the latter whereby said conduit has parallel fluid pressure com v munication paths through the bore of said length of incompressible tubular material and between the outside surface of the length of compressible tubular material and the inside surface of the length of incompressible tubular material.

16. A tamper-proof recording device as set forth in claim 1 wherein said conduit further comprises a flexible armor sheath surrounding said tubular material. 

1. A tamper-proof recording device comprising: a parameter recording instrument; a protective enclosure for said instrument, said enclosure when intact securely protecting said instrument from tampering, and adapted for being secured to apparatus with regard to which a parameter is to be recorded by said instrument; means for securing said enclosure to said apparatus; a conduit adapted to be connected for providing communication between said instrument and said apparatus to cause recording by said instrument of said parameter in response to operation of said apparatus; and connector means for connecting said conduit between said enclosure and said apparatus so as substantially to prevent nondestructive disconnection of said conduit following said connecting thereof, said conduit comprising a length of tubular material, said material being relatively flexible but resisting any substantial twisting thereof, said connector means comprising respective threaded fittings at opposite ends of said material for being respectively threaded to connections at said enclosure and said apparatus, said fittings each having the same thread direction orientation whereby when both are threaded neither of said fittings may be turned in a direction to cause unthreading by loosening thereof withOut causing tightening of the other fitting.
 2. A tamper-proof recording device as set forth in claim 1 wherein said conduit must be destructively disconnected, following connection thereof between said enclosure and said apparatus, to permit disassembly of said enclosure.
 3. A tamper-proof recording device as set forth in claim 1 wherein said connector means comprises a plug and a receptacle, said plug being receivable by said receptacle to connect said conduit to said enclosure, said plug and receptacle cooperating to prevent removal of said plug from said receptacle, when received thereby, while said enclosure is intact.
 4. A tamper-proof recording device set forth in claim 3 wherein said plug is carried at one end of said conduit, said receptacle being positioned at a surface of said enclosure, said plug including latch means preventing removal of said plug from said receptacle when received thereby.
 5. A tamper-proof recording device as set forth in claim 4 wherein said latch means comprises a snap ring, said snap ring expanding in said receptacle to prevent removal of said plug and being releasable only from within said enclosure.
 6. A tamper-proof recording device as set forth in claim 3 wherein said means for securing said enclosure comprises a bracket element adapted for substantially permanent attachment to said apparatus and having an aperture generally in alignment with said receptacle, said conduit passing through said aperture when said plug is received by said receptacle to prevent removal of said enclosure from said apparatus.
 7. A tamper-proof recording device as set forth in claim 1 wherein the instrument is an elapsed-time meter, said enclosure including means responsive to fluid pressure for causing operation of said meter, said conduit providing fluid pressure communication between said apparatus and the fluid pressure-responsive means.
 8. A tamper-proof recording device as set forth in claim 1 wherein said conduit provides fluid pressure communication between said apparatus and a fluid pressure-responsive means included in said enclosure and wherein said tubular material is relatively compressible and elastic and wherein said conduit further includes a length of relatively incompressible yet flexible tubular material extending through the bore of the compressible tubular material whereby clamping of said conduit causes substantial deformation of only said compressible tubular material and said clamping is substantially precluded from interrupting said fluid pressure communication.
 9. A tamper-proof recording device as set forth in claim 1 wherein said conduit provides fluid pressure communication between said apparatus and a fluid pressure-responsive means included in said enclosure and wherein said tubular material is relatively compressible and elastic and wherein said conduit further includes a length of relatively incompressible yet flexible material extending through the bore of said tubular material and having a generally circular cross section of outside diameter less than the diameter of said bore, whereby upon the application of compressive forces to said conduit the tubular material may engage both sides of the incompressible material in the plane of said compressive forces but will not completely engage the entire circumference of said incompressible material so that interruption of said fluid pressure communication is substantially precluded.
 10. A tamper-proof recording device as set forth in claim 9 wherein the incompressible material comprises steel tubing.
 11. A tamper-proof recording device as set forth in claim 7 wherein said elapsed-time meter is electrically powered, said enclosure including an electric power source for powering said meter, the fluid pressure-responsive means comprising a fluid pressure switch connected in a circuit with said power source and said meter.
 12. A tamper-proof time interval recording device comprising: an elapsed-time recording means adapted for being operated in resPonse to fluid pressure; a protective enclosure for said recording means, said enclosure when intact securely protecting said recording means from tampering, and adapted for being secured to apparatus with regard to which an operating time is to be recorded by said recording means; means for securing said enclosure to said apparatus; a relatively flexible conduit adapted to be connected for providing fluid pressure communication between said recording means and said apparatus to cause operation of said recording means in response to operation of said apparatus, said conduit resisting twisting of one end thereof with respect to the other; and connector means including respective threaded fittings at the ends of said conduit for being respectively threaded to provide connections at said enclosure and at said apparatus, said fittings each having the same thread direction orientation whereby when both are threaded to provide said connections neither of said fittings may be turned in a direction to cause unthreading by loosening thereof without causing tightening of the other fitting.
 13. A tamper-proof time interval recording device as set forth in claim 12 further comprising means for substantially preventing clamping of said conduit from interrupting said pressure communication.
 14. A tamper-proof time interval recording device as set forth in claim 12 wherein said connector means comprises a plug and a receptacle, said plug being receivable by said receptacle following threading of said fittings, said plug and receptacle cooperating to prevent removal of said plug from said receptacle, when received thereby, and to prevent twisting of said plug and receptacle with respect to one another.
 15. A tamper-proof recording device as set forth in claim 8 wherein the length of incompressible tubular material is shorter than the length of compressible tubular material with the outside diameter of the former being less than the inside diameter of the latter whereby said conduit has parallel fluid pressure communication paths through the bore of said length of incompressible tubular material and between the outside surface of the length of compressible tubular material and the inside surface of the length of incompressible tubular material.
 16. A tamper-proof recording device as set forth in claim 1 wherein said conduit further comprises a flexible armor sheath surrounding said tubular material. 